feat: configure embedding request size and timeout in Search settings

[KGESH]

What & why

Semantic search embeds documents with a fixed batch size, per-request character budget, and a 30s per-document timeout. Those are fine for a hosted OpenAI-compatible endpoint, but a local embedding server is much slower — on my Ollama setup indexing kept failing on that hardcoded timeout, with no way to raise it short of patching the installed OpenKnowledge bundle.

This exposes the three knobs in Settings → This project → Search:

Field	Config key	Default
Maximum text chunks per indexing request	search.semantic.maxBatchSize	96
Character budget per indexing request	search.semantic.maxBatchChars	96000
Indexing request timeout (seconds)	search.semantic.docTimeoutMs	30 s (30000 ms)

packages/server/src/embeddings/embedder.ts already accepted all three as options — they just had no config-schema entry and no Settings path. Clearing a field resets it to the shipped default. These are overrides for unusual endpoints, not presets; the defaults stay the recommendation for everyone else.

The fields sit as a sibling of the existing Custom endpoint disclosure rather than inside it: they apply to whatever endpoint is in use, the default one included, so nesting them would hide them from everyone who never set a custom endpoint. Each disclosure auto-expands when it has an override, so a value set from the CLI is never invisible in Settings.

Collapsed — a sibling of Custom endpoint	Expanded — the three fields at their defaults

How this was verified

Rebased on main at 70a8e0c.

• pnpm run check (lint, typecheck 11/11, build, tests) — 3633/3634 passed. The one failure is packages/core/src/y-prosemirror-patch.test.ts → "dep-tree invariant: no destructive delete in any shipped bundle", which walks node_modules and hit its 30s limit while the desktop pty-flood test (28.6s) ran concurrently. It passes standalone in 8.2s and is untouched by this change.
• Scoped runs: packages/core config 522 passed · packages/server embeddings + api-search-semantic-factory 111 passed · packages/app settings 223 passed.
• Tests added/updated: SearchSection.dom.test.tsx, settings-search-index.test.ts, core/src/config/schema.test.ts, schema-jsonschema.test.ts, field-registry.test.ts, server/src/embeddings/{embedder,semantic-config,semantic-search-service}.test.ts, plus a tests/stress/settings-search.e2e.ts case.
• Docs: docs/content/reference/configuration.mdx step 4, framed as an override rather than a recommended preset.
• Changeset: .changeset/configure-embedding-transport.md.

26 of the 50 changed files are generated lingui catalogs under packages/app/src/locales/ — pnpm run i18n reproduces them with zero drift. New msgids land with empty msgstr for non-English locales, leaving them to the usual translation pass.

Checklist

• Ran pnpm check (lint, typecheck, tests) locally
• Added a changeset (pnpm changeset) if this changes behavior
• Updated docs if this changes a user-facing surface
• I have read CONTRIBUTING.md and agree to license my contribution under the project's terms (CLA)

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All committers have signed the CLA.

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